1. Field of the Invention
The present invention relates to an auxiliary gasline-heating unit. More particularly, the present invention relates to an auxiliary gasline-heating unit employed in a chemical vapor deposition apparatus.
2. Description of the Related Art
In a conventional chemical vapor deposition apparatus, gases. comprising a He (helium) carrier gas, a N2 (nitrogen) gas, a He-dilute gas, and a Ti[N(CH3)2]4 (TDMAT) vapor, are delivered by a gasline system comprising a TDMAT ampule 10, a He carrier gasline 12 connected to the TDMAT ampule 10, and a mixture gasline 14 connected to the TDMAT ampule shown as in FIG. 1. The mixture gasline 14 further comprises a N2 gasline 16 and a He-dilute gasline 18. The flow rate of the N2 gas and the He-dilute gas can be controlled by the mass flow controller 2 (MFC 2) and the mass flow controller 3 (MFC 3), respectively, and the flow rate of the He carrier gas can be controlled by the mass flow controller 1 (MFC1). Thus, the TDMAT vapor carried by the He carrier gas mixes with the N2 gas and the He-dilute gas through the gasline system after the He carrier gas passes through the TDMAT ampule 10.
However, in general, the exit temperature of the mixture of the N2 gas and the He-dilute gas is about 25xc2x0 C., and the temperature of the TDMAT vapor carried by the He carrier gas is about 50xc2x0 C.; thus, when the TDMAT vapor, the N2 gas and the Hedilute gas are mixed together, the temperature of the mixture is lowered from 50xc2x0 C. to about 32xc2x0 C. As a result, the TDMAT vapor is condensed in the vicinity of a valve PV 8. The condensed TDMAT can pollute the gasline system.
According to the above, the invention provides an auxiliary gasline-heating unit to prevent the TDMAT vapor from condensing in the gasline system of a chemical vapor deposition apparatus.
According to the invention, a gasline system provided for delivering gases for chemical vapor deposition comprises a Ti[N(CH3)2]4 ampule, a carrier gasline connected to the Ti[N(CH3)2]4 ampule, and a mixture gasline consisting of a nitrogen (N2) gasline and a helium(He)-dilute gasline. The mixture gasline connects to the Ti[N(CH3)2]4 ampule in order to mix the carrier gas and the Ti[N(CH3)2]4 with the mixed gas comprising the nitrogen gas and the helium-dilute gas. The improvement in this system comprises either placing an auxiliary gasline-heating unit on an exit of the mixed gas to increase an exit temperature of the mixed gas , or placing auxiliary gasline-heating units on the nitrogen gasline and on the helium-dilute gasline to increase exit temperatures of the nitrogen gas and the helium-dilute gas, respectively.
Thus, the exit temperature of the mixture of the nitrogen gas and the helium-dilute gas is increased; as a result. the temperature when the TDMAT vapor mixes with the nitrogen gas and the helium-dilute gas is increased. That is, the invention can prevent the TDMAT vapor from being condensed.
It is to be understood that both the foregoing general description and the following detailed description are exemplary, and are intended to provide further explanation of the invention as claimed.